Process of making acetic acid



` July 30, 1935. l G. H. FOSTER 2,009,838

PROCESS QF MAKING ACETIC ACID Filed July 22, K 195o aucuns Patented July 3o, 1935 PROCESS F MAKING ACETIC ACD. George H. Foster, Cranford, N. J.,a'ssignor to a corporation of Maine American Cyanamid Company, New York, N. Y.,

Application July 22, 1930,' Serial No. 469,727

V11 Claims. (Cl. 26o-116) I This invention relates to the continuous manufacture of acetic acid by the oxidation of acetaldehyde.

In processes heretofore described in the liter- 5 ature, it has been proposed to oxidize acetaldehyde by means of a gas containing such as air, the acetaldehyde and free oxygen,

air passing through a reacting vessel in a counter-current lso manner. Such processes have been difficult to.

comparatively high in acetaldehyde. The principal objects of this in therefore, the carrying out of the vention are, oxidation of acetaldehyde in a continuous manner, With the production of mini-mum quantities of and to so treat the acetic acid as formic acid, fast as producedas to free the same from contained acetaldehyde and to return the latter to the reaction Vessel. Other important objects are the carrying out of such a process under substantially constant temperature and pressureA conditions and to reduce the hazard of flre and explosion to a minimum.

I have discovered that acetic acid duced substantially continuouslyY by the oxidation of acetaldehydein the may be procarrying out liquid phase,

either with or 'without a catalyst, such as-manganese acetate or the like, by feeding simultaneously theloxygen-containing gas, acetaldehyde and catalyst, where the latter is used, to a substantially single chamber reaction vessel, ,while maintaining the .charge at a uniform temperature and pressure. By regulating within the reaction vessel so that of acetaldehyde vaporized will remove .the heat the pressure the amount of reaction, the temperature of the exothermic reaction may be controlled toa nicety. Means.

are provided for automatically removing the produced acetic acid from the reaction vessel as fast as formed. It is'here proposed to acetic acid from the reaction vessel trator tted with means for maintaining anA conduct the to a concenacetaldehyde vaporizing temperature -and to there remove contained acetaldehyde. This vaporized material-then passes to condensers, from which the condensed acetaldeliyde to the reaction kettle.

is returned There is illustrated in the-drawing a diagrammatic` view of an apparatus for carrying out the invention.

Referring now with particularity to the dia- Y grammatic drawing, there is shown at I a reaction kettle having a single chamber and into which acetaldehyde may be fed through the pipe 2 from the feed tank 3. The feed tank may be continuously or intermittently supplied with additional acetaldehyde by the supply line 4, y'as 10 desired. Where acatalyst is found necessary or desirable, it may be fed into the reaction kettle I through the same supply line for the acetaldehyde or separately therefrom, as desired. The reaction kettle is provided with any desired .15 means for maintaining a constant temperature and pressure therein, such as steam coils, and/or cooling coils, and/or a pump, not shown, as all of these elements'are well-known in the art.

An inlet pipe 5 is provided near, the bottom oi 20 the reaction kettle I through which air or other free oxygen-containing gas may be introduced for the oxidation of the acetaldehyde.

A vapor line 6, extending from the top of the reaction kettle, extends to a water-cooledA con- 25 denser 1 and any uncondensed acetaldehyde passes on through the pipe 8 to the water or brine cooled condenser 9. Fromthe latter condenser the uncondensed gas passes through a pressureregulating valve I0 and into the bot- 30 tom of a scrubber Il countercurrent to a. ow of water entering at I2, and is vented at I3, preferably through a gas meter or the like. Acetaldehyde condensed in the condensers 1 and 9 is Vreturned by means of pipes I4 and l5, respec- 35 tively, into the reaction kettle. I for further' oxidation. An equalizing line I6V may be provided between the vapor take-ott B and top of the acetaldehyde feed tank 3 to communicate the system pressure to the feed tank 3.

An acetic acid take-oft pipe is shown at I 1 nearA the bottom of the reaction kettle and passes upwardly therefrom into a concentrator Il fitted with steam coils, not shown, for the purpose of producing an acetaldehyde vaporizing temperay4,5 ture therein. The acetaldehyde contained in the' produced aceticv acid, vaporized by the steam coils, passes upwardly through the take-olif I!AV into the vapor line B where it passes to the condensers alongwi'th any vaporized acetaldehyd 50 from the reaction kettle. A` concentrated acetic acid linevis shown at 20, extending from some' suitable point 'in the concentrato'r I8 upwardly to form a goose-neck' 2l and then downwardly into the concentrated acetic acid receiver 22,

which is maintained at the system pressure. In most instances it will be found desirable to conduct the acetaldehyde-free acetic acid from the receiver 22 through the line 23 to a continuous rectication apparatus where any desired concentration of acetic acid may be produced, all of which is well-known.

In operating the process according to this invention, a charge of liquid acetaldehyde, or of whereupon the oxidation of acetaldehyde to acetic acid begins. The ilow of acetaldehyde through the line 2 into the reaction kettle is continued at substantially the same rateD that acetic acid is formed. By regulating the .pressure within the reaction vessel, the vaporization of acetaldehyde is controlled, which in turn determines the reaction temperature by removing the heat of reaction to any desired degree.- As the acid is formed and as the acetaldehyde is fed intothe kettle, the acetic acid overiiows automatically through the pipe I'I into the concentrator I8. It can readily be calculated, therefore, that the acid in the kettle will remain at a concentration of approximately 50%. Any free acetaldehyde not oxidized passes upwardly through the vapor line 6 into the condensers 'I and 9, from which it is returned as a condensate to the reaction kettle for further oxidation.

As the acetic acid is produced, the concentrator I8 gradually illls and any contained acetaldehyde therein is boiled oil by means of the steam coils therein, the vaporized acetaldehyde being conducted into the vapor line 6 and into the condensers as before. Due tothe fact that the outlet 20 for the concentrated acetic acid is provided With the goose-neck 2i, the level of liquid within the concentrator is maintained at a constant point and concentrated acetic acid automatically flows from the concentrator to the receiver as fast as formed. In order to prevent a syphoning action through the goose-neck, a vent 24 is provided connecting the upper part of the goose-neck with the vapor line 8. In order to prevent a gas lock in this portion of the apparatus, a vent 25 is likewise provided between the receiver 22 and the vapor line 8.

The uncondensed gases from the condensers 1 and 8 pass through the pressure regulating valve I0 at any desired rate as it will be apparent that this control valve will determine the pressure within the kettle and the rate of take-oir of acetaldehyde and other vapors therefrom. These uncondensed gases pass upwardly throughv the scrubber II countercurrent to a iiow of water or other scrubbing liquid and are vented at I 3, preferably through a gas meter, for control purposes. The eflluent from the scrubber may be caught as through the take-off 26 for further disposition as desired.

As a specific example ci operating the 'apparatus shown, a kettle may be charged with a quantity of acetaldehyde and acetic acid in equal weights suilicient to li the same to the desired level, which will be determined by the location of the upper part of the pipe I1. This likewise initially fills the concentrator to this point. In

aocaeas The kettle having been charged as above de-' scribed, the temperature thereof is thenralsed to C. while the pressure is raised to 50 lbs. per sq. in. Air may' then be admitted through the pipe 5 at a rate ofapproximately 30 cubic feet per minute' of free air, and the pressure regulating valve I0 opened to the point required to allow a corresponding flow. Acetaldehyde is run in through the supply line 2 at a rate aimaient to cause the kettle temperature to remain constant while the pressure is maintained at substantially 50 lbs. per sq. in. As acetic acid ic being formed in the reaction kettle, the same will overiiow into the concentrator, and a temperature being maintained in that portion of the apparatus sufllcient to vaporize the acetaldehyfle, to wit, 105 C., the acetic acid is rendered substantially acetaldehyde-free and automatically overflows vthrough the goose-neck 2l from the concentrator to the receiver and this flow is maintained as fast as the concentrated acid is formed.

By maintaining the steam coils in the concentrator at the above temperature, the acetaldehyde content of the acetic acid has been reduced to less than 10% so that the acid overflowing in the receiver is thus obtained at. a strength of substantially The vaporized acetaldehyde from the concentrator is returned to the reacting kettle from the condensers, as above set forth.

From the above, it will be apparent that the invention permits, the continuous oxidation of acetaldehyde to acetic acid in such a manner as to produce larger quantities of acetic acid in a given time with a given piece of apparatus, than has heretofore been possible. Moreover, the production of a higher grade of acetic acid, relatively free from acetaldehyde and formic acid, due

to over-oxidation, is here set forth. Likewise, in-

asmuch as it is possible to obtain anapparatus for the continuous distillation and rectification of acetic acid, I am able to conduct the operations of oxidation and rectiiication expeditiously and without the use of any considerable intermediate storage for the crude acetic acid. inasmuch as the kettle liquor is of practically constant comW position containing a lower concentration of acetaldehyde than has been heretofore required, the danger of explosion and fire is reduced to a min- Analysis of the vented gas passing throughthe outlet I3 shows that the equipment removes oxygen from the air in practically quantitative amounts. Due to the layout of condensers, any acetaldehyde vaporized in the kettle through the exothermic reaction, is recovered and returned to the kettle wlthoutloss.

While the invention has been shown and described with particular reference to the production of acetic acid by the use of certain temperatures, pressures, and other operations, yet obviously I do not wish to be limited thereto, but the invention is to be construed broadly and restricted only by the scope of the claims.

1. A method of producing acetic acid by the oxidation of acetaidehyde, which includes the steps of causing a reaction between an oxidizing gas and liquid acetaldehyde, and vaporizing sufficient quantities of acetaldehyde from the rereaction kettle, maintaining the kettle charge under constant temperature through vaporization of requisite quantities of acetaldehyde, and continuously removing the acetic acid formed.

4. A method of continuously producing acetic acid which comprises continuously flowing acetaldehyde and a gas containing free oxygen to a reaction kettle, maintaining the kettle charge at substantially 80 C. and 50 lbs. per sq. in., and continuously removing the acetic acid formed.

Y 5.. A-method of continuously producing acetic acid which comprises continuously flowing acetaldehyde and a gas containing free oxygen to a reaction kettle, maintaining the kettle charge i under constant temperature by vaporization of requisite quantities of acetaldehyde, cpntinuously removing the acetic acid formed, continuously removingacetaldehyde from the crude acetic acid, condensing both the acetaldehyde removed from the crude acetic acid and that escaping from the kettle due to the heat of reaction, and returning the condensed acetaldehyde to the reaction kettle. i

6. A method of continuouslyproducing acetic acid which comprises maintaining a charge of.

equal parts of acetaldehyde and acetic acid at a temperature of 80 C. and under substantially 50 lbs. pressure, continuously adding 'acetaldehyde and an oxygen-containing gas to the charge, continuously removing the acetic acid formed to a concentrator, continuously removing contained acetaldehyde from the. acetic acid in the concentrator and returning the thus removed acetaldehpde to the reaction kettle.

'1. A continuous method of producing acetic acid which comprises continuously owing acetaldehyde and a gas containing free oxygen counter-current through a reaction kettle, maintaining a heated reaction zone in said kettle in which the acetaldehyde is oxidized to acetic acid, continuously removing acetaldehyde containing acetic acid from said kettle, passing said mixture through a zone outside said kettle, the temperature of which is above the vaporization point of the acetaldehyde in the acetaldehyde-acetic acid mixture, whereby the acetaldehyde is vaporized, condensing the thus separated acetaldehyde and returning the same to the reaction zone, and continuously removing the acetaldehyde free acetic acid.

8. A method of continuously producing acetic acid which comprises passing the charge of equal parts of acetaldehyde and acetic acid through a reaction zone, continuously adding acetaldehyde and oxygen containing gas to said charge, continuously removing the acetic acid formed to a concentrator, continuously removing the contained acetaldehyde from the acetic acid in the concentrator, and returning the thus removed acetaldehyde to the reaction kettle.

9. A continuous method of producing acetic acid which comprises continuously flowing liquid acetaldehyde and a gas containing free oxygen through a reaction kettle, maintaining a heated reaction zone in said kettle in which the acetaldehyde is oxidized to acetic acid, continuously removing acetaldehyde containing acetic acid from said kettle, passing said mixture through a zone outside of said kettle, the temperature of which is above the vaporization point of the acetf aldehyde in the acetaldehyde-acetic acid mixture, whereby the acetaldehyde'is vaporized, condensing the thus separated acetaldehyde and returningi the same to the reaction' zone, and ycontiniously removing the acetaldehyde free acetic ac1 10. A process for the continuous production of acetic acid by oxidizing acetaldehyde in a liquid phase and continuously replacing a portion of the reaction liquor by fresh acetaldehyde characterized in that the concentration of acetic acid in the reaction liquor is maintained at approximately 50% and acetic acid is separated from the withdrawn reaction liquor.

11. A method of`continuously producing acetic acid which comprises continuously flowing acetaldehyde and ya gas containing free oxygen to a reaction zone maintained ata reaction temperature whereby the acetaldehyde is oxidized and continuously removing the acetic acid from the reaction zone at substantially the rate at which it is formed.

. GEORGE H. FOSTER. 

